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Noise in narrow band meausrement

Question asked by beatouyoo on Nov 1, 2011
We are considering to buy a used Agilent 8560E spectrum analyzer. But before that, I still have some questions. I have a small high frequency signal, ~ 100nA 1GHz, that is sent into a transimpedance amplifier. The amplifier is 50ohm matched in both input and output, and its N.E.P is 20pA/rt.Hz. This means the input noise floor at 1GHz is 632nA, at 1MHz 20nA, and at 1Hz is 20pA. The transimpedance gain is 1M ohm. If I set the span in the spectrum analyzer to a very narrow bandwidth, say, 10Hz, can the spectrum analyzer recover the signal from the broadband noise? Thank you very much.